US8160465B2 - Image forming apparatus and control method thereof - Google Patents
Image forming apparatus and control method thereof Download PDFInfo
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- US8160465B2 US8160465B2 US13/155,511 US201113155511A US8160465B2 US 8160465 B2 US8160465 B2 US 8160465B2 US 201113155511 A US201113155511 A US 201113155511A US 8160465 B2 US8160465 B2 US 8160465B2
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- 238000012546 transfer Methods 0.000 claims abstract description 326
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- 230000008859 change Effects 0.000 abstract description 26
- 230000005684 electric field Effects 0.000 abstract description 17
- 238000012360 testing method Methods 0.000 description 19
- 230000007547 defect Effects 0.000 description 14
- 238000011161 development Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- 230000008569 process Effects 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 2
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
- G03G15/16—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
- G03G15/1605—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using at least one intermediate support
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G2215/00—Apparatus for electrophotographic processes
- G03G2215/16—Transferring device, details
- G03G2215/1604—Main transfer electrode
- G03G2215/1623—Transfer belt
Definitions
- An apparatus and a method of the present general inventive concept relate to an image forming apparatus and a control method thereof, and more particularly, to an image forming apparatus and a control method thereof to improve quality of an image when a change in posture of a print media occurs.
- An image forming apparatus refers to an apparatus for forming an image corresponding to print data on print paper and encompasses a copy machine, a printer, a scanner, a facsimile, a multifunction copier with integrated functions of these machines, or other machines.
- FIG. 1 shows a path of a print medium which is being conveyed according to a single-sided print mode in an electro-photographic image forming apparatus 1 employing an indirect electro-photographic system.
- a print medium picked up by a pickup roller (not illustrated) is conveyed between a transferred unit 20 and a transferring unit 10 through a feed roller 2 and a registration roller 3 .
- a visible image formed of a toner is formed on an image carrier 5 .
- the transferred unit 20 includes an intermediate transfer belt 21 , driving rollers 23 , 24 and 25 for driving the intermediate transfer roller 21 , and a transfer belt roller 22 for transferring the visible image of the image carrier 5 onto the intermediate transfer belt 21 .
- the visible image transferred onto the intermediate transfer belt 21 of the transferred unit 20 is transferred into the print medium passing between the transferred unit 20 and the transferring unit 10 .
- a voltage supplying unit (not illustrated) applies a transfer voltage having the opposite polarity to the toner to the transferring unit 10
- a transfer electric field is produced between the transferred unit 20 and the transferring unit 10 .
- the toner forming the visible image is transferred onto the print medium by this transfer electric field.
- the visible image transferred onto the print medium is fixed on the print medium while passing through fixing rollers 11 and 12 that form a fixing unit 13 , and is discharged through discharge rollers 14 and 15 to the outside.
- a posture, that is, an entrance angle, of the print medium may be changed.
- Such change of the entrance angle of the print medium may be caused by a variety of factors including a difference in rotation speed between multiple rollers arranged before and after pass of the print medium through the transferred unit 20 and the transferring unit 10 , ambient environment conditions (temperature/humidity), thickness of the print medium, etc.
- a feature of transfer of the toner onto the print medium by the transfer electric field may be varied, which may result in an effect on print quality.
- such change of the entrance angle may cause image defects such as variation of concentration of the image formed on the print medium, lack of toner in a portion of the image, etc.
- FIG. 2 shows a double-sided print path of the image forming apparatus 1 of FIG. 1 , in which the single-sided printed print medium is conveyed along a double-sided print path DP as the discharge roller 14 is reversely rotated.
- the conveyed print medium again passes between the transferred unit 20 and the transferring unit 10 by means of a conveying roller 4 and the registration roller 3 , a new visible image is formed on a rear side of the print medium.
- the double-sided print path DP is more curved than a single-sided print path SP. Accordingly, when the print medium conveyed along the double-sided print path passes through the transferred unit 20 and the transferring unit 10 , a posture of the print medium may be changed in a pattern different from that in the single-sided print and an image defect or a change in concentration of an image may be caused in a manner different from that of the single-sided print.
- the present general inventive concept can provide an image forming apparatus and a control method thereof to improve quality of an image when a change in posture of a print media occurs in the image forming apparatus.
- the present general inventive concept can also provide an image forming apparatus and a control method thereof to adjust concentration of an image formed on a printed medium.
- An example embodiment of the present general inventive concept can be achieved by providing an image forming apparatus including a transferring unit to form a visible image on a transferred medium, a bias supplying unit to supply bias to the transferring unit, and a controller to control the bias supplying unit to supply first to third biases to the transferring unit to form the visible image on the transferred medium.
- the controller may control the bias supplying unit to supply the first to third biases to the transferring unit while at least first to third regions of the transferred medium pass a transfer region at which the visible image is formed, respectively.
- the first to third regions may correspond to a leading end region, a middle region and a tail end region of the transferred medium on the basis of a travel direction of the transferred medium, and an absolute value of the second bias may be larger than an absolute value of the first bias and an absolute value of the third bias may be smaller than the absolute value of the first bias.
- the first to third regions may correspond to a leading end region, a middle region and a tail end region of the transferred medium on the basis of a travel direction of the transferred medium, and an absolute value of the second bias may be larger than an absolute value of the first bias and an absolute value of the third bias may be larger than the absolute value of the second bias.
- the first to third regions may correspond to a leading end region, a middle region and a tail end region of the transferred medium on the basis of a travel direction of the transferred medium, and an absolute value of the second bias may be smaller than an absolute value of the first bias and an absolute value of the third bias may be smaller than the absolute value of the second bias.
- the first to third biases may be capable of being varied depending on at least one of ambient temperature/humidity, thickness of the transferred medium, use time of the transferring unit and a print mode of the transferred medium.
- Exemplary embodiments of the present general inventive concept can also be achieved by providing an image forming apparatus including a transferred unit on which a visible image is formed, a transferring unit to form a transfer region through which the visible image is transferred onto a print medium, along with the transferred unit, a bias supplying unit to supply bias to the transferring unit so that a transfer electric field is produced in the transfer region nip, and a controller to control the bias supplying unit to supply different biases to the transferring unit in correspondence to a change of posture of the print medium while the print medium passes through the transfer region nip.
- the controller may control the bias supplying unit to supply a second bias having an absolute value smaller than that of a first bias of the normal path to the transferring unit.
- the second bias may be varied depending on at least one of ambient temperature/humidity, thickness of the print medium, use time of the transferring unit and a print mode of the print medium.
- the controller may control the bias supplying unit to supply a third bias having an absolute value larger than that of the first bias of the normal path to the transferring unit.
- Exemplary embodiments of the present general inventive concept can also be achieved by providing a control method of an image forming apparatus including a transferred unit on which a visible image is formed, and a transferring unit to form a transfer region through which the visible image is transferred onto a print medium, along with the transferred unit, the control method including sensing an attribute of the print medium, and supplying different first to third biases to the transferring unit while at least first to third regions of the print medium pass through the transfer region nip, according to the attribute of the print medium.
- the at least first to third regions of the print medium may be divided based on whether an entrance angle of the print medium into the transfer region and the transfer electric field are changed while the print medium passes through the transfer region nip.
- the first to third regions may correspond to a leading end region, a middle region and a tail end region of the print medium on the basis of a travel direction of the print medium, and an absolute value of the second bias may be larger than an absolute value of the first bias and an absolute value of the third bias may be smaller than the absolute value of the first bias.
- the first to third regions may correspond to a leading end region, a middle region and a tail end region of the print medium on the basis of a travel direction of the print medium, and an absolute value of the second bias may be larger than an absolute value of the first bias and an absolute value of the third bias may be larger than the absolute value of the second bias.
- the first to third regions may correspond to a leading end region, a middle region and a tail end region of the print medium on the basis of a travel direction of the print medium, and an absolute value of the second bias may be smaller than an absolute value of the first bias and an absolute value of the third bias may be smaller than the absolute value of the second bias.
- the first to third biases may be varied depending on at least one of ambient temperature/humidity, thickness of the print medium, use time of the transferring unit and a print mode of the print medium.
- Exemplary embodiments of the present general inventive concept can also be achieved by providing a control method of an image forming apparatus including a transferred unit on which a visible image is formed, and a transferring unit to form a transfer region through which the visible image is transferred onto a print medium, along with the transferred unit, the control method including applying a first bias to the transferring unit, maintaining the first bias in the transferring unit if a posture of the print medium is not changed, and applying a second bias different from the first bias to the transferring unit if the posture of the print medium is changed.
- the applying a second bias may include applying second bias having an absolute value smaller than that of the first bias to the transferring unit.
- the second bias may be varied depending on at least one of ambient temperature/humidity, thickness of the print medium, use time of the transferring unit and a print mode of the print medium.
- the applying second bias may include applying a third bias having an absolute value larger than that of the first bias to the transferring unit.
- Exemplary embodiments of the present general inventive concept can also be achieved by providing a transfer unit of an image forming apparatus, including a transfer region to transfer an image to a print medium, and a bias supplying unit to selectively apply a plurality of transfer biases to the transfer region based on an attribute of the print medium passing through the transfer region.
- the attribute can include at least one of an entrance angle of the print medium, a distance from the transfer region to a leading edge of the print medium, a print mode of the image forming apparatus, a thickness of the print medium, a speed of the image forming apparatus, and an ambient condition of the image forming apparatus.
- the transfer unit can further include guide plates to control the entrance angle of the print medium.
- the transfer unit can further include an input unit to receive an input signal from a user, and a controller to control the bias supplying unit based on the input signal.
- Exemplary embodiments of the present general inventive concept can also be achieved by providing a method of transferring an image to a print medium, the method including selectively applying a plurality of transfer biases to a transfer region based on an attribute of the print medium passing through the transfer region.
- FIG. 1 is a schematic view illustrating a convey path of a print medium along a single-sided print path of a conventional image forming apparatus.
- FIG. 2 is a schematic view Illustrating a convey path of a print medium along a double-sided print path of the image forming apparatus of FIG. 1 .
- FIG. 3 is a schematic sectional view of an image forming apparatus according to an embodiment of the present general inventive concept.
- FIG. 4 is a schematic block diagram of the image forming apparatus of FIG. 3 .
- FIG. 5 is an enlarged view illustrating a main part of the image forming apparatus of FIG. 3 .
- FIG. 6 is a view illustrating a guide plate to guide a transferred unit and a transferring unit to a print medium.
- FIG. 7 is a view illustrating a result of a test to measure positions of lack of image in a thin print medium.
- FIG. 8 is a view illustrating a result of the test when a transfer voltage is raised to correct lack of image in FIG. 7 .
- FIG. 9 is an exemplary timing diagram of a transfer voltage to allow removal of the image defect illustrated in FIGS. 7 and 8 .
- FIG. 10 is a view illustrating a result of a test to measure positions of lack of image in a thick print medium.
- FIG. 11 is an exemplary timing diagram of a transfer voltage to allow removal of the image defect illustrated in FIG. 10 .
- FIG. 12 is a view illustrating a pattern of a transfer voltage to be applied to a leading end, a middle portion and a tail end of a print medium depending on system resistance of a thick print medium.
- FIG. 13 is a view illustrating a result of a test when another transfer voltage is applied to a tail end of a print medium depending on change of ambient temperature/humidity.
- FIG. 14 is an exemplary view illustrating a pattern of a transfer voltage to be applied to a transferring unit while a leading end, a middle portion and a tail end of a general print medium pass through a transfer region, depending on system resistance under conditions of normal temperature and normal humidity.
- FIG. 15 is an exemplary view illustrating a pattern of a transfer voltage to be applied to a transferring unit while a leading end, a middle portion and a tail end of a general print medium pass through a transfer region, depending on system resistance under conditions of low temperature and low humidity.
- FIG. 16 is another exemplary timing diagram of the transfer voltage of FIG. 11 .
- FIGS. 17A and 17B are flow charts of a control method of an image forming apparatus according to an embodiment of the present general inventive concept.
- FIG. 18 is a flow chart of a control method of an image forming apparatus according to another embodiment of the present general inventive concept.
- the image forming apparatus 100 can include development cartridges 120 , an exposure unit 170 , a transferred unit 130 , a transferring unit 140 , a bias supplying unit 185 and a controller 190 .
- Each of the development cartridges 120 can include a charging roller 124 , an image carrier 121 , a developing roller 125 , and a cartridge case (not illustrated) to accommodate the charging roller 124 , the developing roller 125 and the image carrier 121 .
- the development cartridges 120 may include four development cartridges to store CMYK (C: cyan, M: magenta, Y: yellow and K: black) toners (developers), respectively.
- the number of development cartridges 120 may be varied as necessary.
- a monochromatic image forming apparatus may include one development cartridge 120 to store the black toner and a color image forming apparatus may include three development cartridges to store the CMY toners except the black toner, respectively.
- the image carrier 121 can be charged to a surface potential by the charging roller 124 , and the exposure unit 170 can expose the surface of the charged image carrier 121 so that an electrostatic latent image corresponding to a desired image can be formed on the surface.
- the developing roller 125 can develop the electrostatic latent image with a color toner stored in the development cartridge 120 so that a visible image of the color toner can be formed on the surface of the image carrier 121 .
- the visible image formed on the surface of the image carrier 121 can be transferred onto the transferred unit 130 so that the visible image can be formed on the surface of the transferred unit 130 .
- the visible image can be transferred onto a surface of an intermediate transfer belt 133 of the transferred unit 130 .
- the transferred unit 130 can include the intermediate transfer belt 133 , a pair of intermediate transfer belt driving rollers 131 , intermediate transfer rollers 135 and an idle roller 137 .
- the idle roller 137 may be omitted.
- the intermediate transfer rollers 135 can transfer the visible image formed on the image carriers 121 , which face the intermediate transfer roller 135 with the intermediate transfer belt 133 placed therebetween, onto the intermediate transfer belt 133 .
- the visible image can have certain color, for example, cyan color. While the intermediate transfer belt 133 on which the visible image of the cyan color passes through the next development cartridge 120 and the next intermediate transfer roller 135 , the visible cyan color image can be overlaid with a visible image of a different color, for example, yellow color. In this manner, while passing through two remaining development cartridges, the visible cyan and yellow color image on the intermediate transfer belt 133 can be overlaid with visible images of a remaining different color, for example, magenta and/or black color. As a result, a full color visible image can be formed on the intermediate transfer belt 133 .
- the formed full color image can be transferred onto a print medium, which passes between the transferred unit 130 and the transferring unit 140 , by means of the transferring unit 140 .
- a print medium may also be referred to as a transferred medium.
- the print medium can be loaded on a paper feed cassette 110 , picked up by a pickup roller 111 , and then conveyed to a registration roller 166 by means of conveying rollers 113 and 115 .
- the registration roller 166 can register a leading end of the conveyed print medium and then can convey the registered print medium to a transfer nip N, which will be described later with reference to FIG. 5 , so that the full color visible image can be transferred onto an image region of the conveyed print medium.
- the transfer nip N may also be referred to as a transfer region.
- the transfer region may not be necessarily configured in the form of nips engaging with each other, such as the transfer nip N, but may be configured in other known or later developed shapes to perform toner transfer.
- the transferring unit 140 and the transferred unit 130 can form the transfer nip N together, as shown in FIG. 5 , and a transfer of the visible image onto the print medium can be conducted in the transfer nip N.
- the bias supplying unit 185 can apply a transfer bias to the transferring unit 140 .
- the transfer bias may be at least one of a transfer voltage and a transfer current.
- the controller 190 can control the bias supplying unit 185 to supply the transferring unit 140 with a plurality of different biases, for example, different first, second and third transfer bias, as described herein.
- the first to third bias may be different in magnitude if it is of a DC bias, or may be different in at least one of magnitude and frequency if it is of an AC bias.
- the at least first to third regions can be divided based on whether an entrance angle of the print medium into the transfer nip N is changed or a transfer electric field is changed when the print medium corresponding to the first to third regions passes through the transfer nip N.
- the change of the entrance angle of the regions into the transfer nip N can result in a local change of a posture or a convey path of the print medium.
- the first to third transfer bias may also be varied depending on at least one of ambient temperature/humidity, thickness of the print medium and lifetime of the transferring unit 140 .
- various attributes of the print medium passing through the transfer nip N may be changed.
- one region of the print medium may pass through the transfer nip N along an over-transfer path C in a region A near the transferring unit 140 from the normal path P.
- the print medium may be rapidly charged by bias, that is, by a high transfer voltage applied to the transferring unit 140 .
- an excessive transfer electric field can result from the posture change of one region of the print medium (for example, the change of the entrance angle of the print medium into the transfer nip N).
- the polarity of the toners may be reversed due to the rapid charging of the print medium.
- Such toners with the reversed polarity on the print medium may be reversely transferred onto the intermediate transfer belt 133 by an electric repulsive force, which may result in an image picking effect of the print medium.
- the print medium may be slowly charged, and thus the toners on the intermediate transfer belt 133 may not be fully transferred onto the print medium because of insufficiency of a transfer electric field. Accordingly, an image omission may be observed in one region of the print medium by naked eyes.
- FIG. 6 illustrates guide plates 193 and 195 to guide a print medium to reduce a degree of change of an entrance angle of the print medium into the transfer nip N.
- the arranged guide plates 193 and 195 may be isolated from the transfer nip N, it may not be possible to guide all regions including the leading end to tail end regions to the transfer nip N, and a posture of the print medium may be inevitably changed.
- such change of the posture of the print medium may be caused by combinations of various factors such as a difference in rotation speed between rollers, a difference in path shape between a single-sided print mode and a double-sided print mode, ambient condition such as temperature/humidity, rigidity (thickness) of the print medium, a print speed (ppm) of the image forming apparatus 100 , and so on.
- FIG. 7 illustrates a result of 25 exemplary print tests performed for thin letter-size print medium (60 [g/m 3 ] of basis weight) with a process speed (252.045 mm/sec) by the image forming apparatus.
- a constant transfer voltage was applied to the transferring unit 140 while the print medium was being passed through the transfer nip N.
- the vertical axis represents a distance from a physical leading end of the print medium along a travel direction of the print medium and the horizontal axis represents the number of times of tests.
- Dots plotted in FIG. 7 represent start points E at which image omission is identified by naked eyes.
- first and second tests illustrate that an image is omitted in the print medium at positions apart by 108 mm and 81 mm from leading ends of the print medium, respectively.
- Third to 25 th tests illustrate that image omission begins to be identified by naked eyes in a range of about 81 mm to 126 mm from a leading end of the print medium.
- image omission of 85% can occur in a range of about 90 mm to about 126 mm from the leading end.
- image omission of 100% can occur from a distance exceeding about 126 mm from the leading end.
- FIG. 7 Since the image omission illustrated in FIG. 7 can be caused by insufficiency of an electric field due to the local change of the entrance angle of the print medium into the transfer nip N, as described above, tests were performed using an increase of a transfer voltage applied to the transferring unit 140 to supplement the insufficient transfer electric field
- FIG. 8 illustrates a result of these tests.
- an image picking effect of 100% can occur in a range of a leading end of the print medium to about 9 mm and an image picking effect of 85% or so can occur in a range of about 9 mm to about 63 mm.
- Good image quality can be obtained in a range of the leading end to a distance exceeding about 81 mm with no image picking effect.
- the controller 190 of the image forming apparatus 100 may control the bias supplying unit 185 to apply a transfer voltage illustrated in FIG. 9 to the transferring unit 190 .
- t 1 is a time at which the leading end of the print medium passes through the transfer nip N
- t 2 , t 3 and t 4 are times at which the print medium distant by 9 mm, 63 mm and 81 mm from the leading end passes through the transfer nip N, respectively
- t 5 is a time at which a tail end of the print medium passes through the transfer nip N.
- an entire length of time during which the print medium passes through the transferring unit 140 is denoted in FIG. 8 by an interval between t 1 and t 6 .
- a first transfer voltage V 1 can be applied to the transferring unit 140 in an interval of t 1 to t 2 , that is, while the print medium in a range of the leading end to 9 mm passes through the transfer nip N.
- a second transfer voltage V 2 can be applied to the transferring unit 140 in an interval of t 2 to t 3 , that is, while the print medium in a range of 9 mm to 63 mm passes through the transfer nip N. Since a degree of image picking in the range of the leading end to 9 mm is high, an absolute value of the first transfer voltage V 1 can be smaller than that of the second transfer voltage V 2 . That is, the first transfer voltage can be lower than the second transfer voltage.
- a third transfer voltage V 3 higher than the second transfer voltage V 2 can be applied to the transferring unit 140 in an interval of t 3 to t 4 , that is, while the print medium in a range of 63 mm to 81 mm passes through the transfer nip N.
- a fourth transfer voltage V 4 higher than the third transfer voltage V 3 can be applied to the transferring unit 140 in an interval of t 4 to t 5 , that is, while the print medium in a range of 81 mm to the tail end passes through the transfer nip N.
- the fourth transfer voltage V 4 may be the transfer voltage that provided the good image quality in the range of 81 mm to the tail end in the test of FIG. 8 .
- the transfer voltage timing diagram of FIG. 9 may be derived by reversely lowering a voltage level step by step on the basis of the transfer voltage that provided the good image quality in the test of FIG. 8 .
- leading end region and the tail end region are interpreted to mean that the former precedes the latter with respect to a traveling direction of the print medium, and may not necessarily coincide with physical leading and tail ends of the print medium.
- the leading end region may correspond to a region covering a range from the physical leading end of the print medium to a point exceeding a physical middle region of the print medium. That is, the size of each region may be varied.
- the middle region can be interpreted to mean the remaining region except the leading end region and the tail end region.
- FIG. 10 illustrates a result of a test performed using a print medium of a kind different from that of the print medium tested in FIGS. 7 and 8 .
- the print medium used is a thick letter (163 [g/m 3 ] of basis weight) and a process speed is 126.023 [mm/sec].
- the process speed can be decreased since it generally requires more heat and pressure than a thin print medium in toner fixation. Accordingly, the test of FIG. 10 was performed at a process speed which is about half (126.023 [mm/sec] 25 ppm) as low as that (252.045 [mm/sec]) of FIG. 7 .
- image omission of 85% occurs in a range of about 162 mm to about 216 mm from the leading end.
- image omission of 100% occurs from a distance exceeding about 216 mm to a tail end of the print medium.
- a transfer voltage having a pattern illustrated in FIG. 11 can be applied to the transferring unit 140 .
- an absolute value of a transfer voltage to be applied while the region with the image omission passes through the transfer nip N can be adjusted to be larger than that of a transfer voltage to be applied while the region with the good image quality passes through the transfer nip N.
- a pattern of the transfer voltage illustrated in FIG. 11 can be as follows.
- a first transfer voltage V 5 can be applied in an interval of t 1 to t 2 , that is, while the region of the leading end of the print medium to 126 mm passes through the transfer nip N.
- the first transfer voltage V 5 may be the transfer voltage used for the tests of FIG. 10 .
- a second transfer voltage V 6 having an absolute value larger than that of the first transfer voltage V 5 can be applied to the transferring unit 140 in an interval of t 2 to t 3 , that is, while the region of 126 mm to 162 mm passes through the transfer nip N.
- a third transfer voltage V 7 having an absolute value larger than that of the second transfer voltage V 6 can be applied to the transferring unit 140 in an interval of t 3 to t 4 , that is, while the region of 162 mm to 216 mm passes through the transfer nip N.
- a fourth transfer voltage V 8 having an absolute value larger than that of the third transfer voltage V 7 can be applied to the transferring unit 140 in an interval of t 4 to t 5 , that is, while the region of 216 to the tail end passes through the transfer nip N.
- the print medium may be divided into four regions and different first to fourth transfer voltages may be applied to the transferring units 140 to compensate for an image defect occurring in each of the regions.
- FIG. 16 illustrates a modification of the transfer voltage timing diagram illustrated in FIG. 11
- the controller 180 may control the bias supplying unit 185 to apply a fifth transfer voltage V 9 having an absolute value lower than that of the first transfer voltage V 5 to the transferring unit 140 .
- the controller 190 may control the bias supplying unit 185 to apply a first transfer bias, a second transfer bias having an absolute value larger than that of the first transfer bias, and a third transfer bias having an absolute value larger than that of the second transfer bias to the transferring unit 140 , respectively.
- the predetermined thickness may be about 90 [g/m 3 ] of basis weight and the predetermined speed may be about 12 ppm.
- the predetermined thickness and the predetermined speed may be varied depending on formation of print convey paths, roller arrangement, ambient temperature/humidity, lifetime (use time) of the transferring unit 140 and so on in the image forming apparatus.
- FIG. 12 illustrates a graph of a transfer voltage to be applied to a leading end region, a middle region and a tail end region of a print medium depending on system resistance.
- the leading end region may be assumed to correspond to a region from the leading end of the print medium to a distance of about 10 mm to about 20 mm and the tail end region may be assumed to correspond to a region from the tail end of the print medium to a distance of about 10 mm to about 20 mm.
- the leading and tail end regions are not necessarily limited to these regions but may be varied depending on the presence or absence of the guide plates 193 and 195 , their arrangement angle and length and/or other design characteristics of the print medium and transfer mechanisms.
- the print medium is thick paper of about 163 [g/m 3 ] of basis weight and the convey speed of the print medium is about 5 ppm (24.75 mm/sec) which corresponds to only 20% of the convey speed (126 mm/sec) of the print medium in FIGS. 10 and 11 .
- a leading end transfer voltage (the first transfer bias), the middle transfer voltage (the second transfer bias) and the tail end transfer voltage (the third transfer bias) may be applied to the transferring unit 140 while the leading end region, the middle region and the tail end region of the print medium pass through the transfer nip N, respectively, as illustrated in FIG. 12 .
- an absolute value of the middle transfer voltage (the second transfer bias) can be larger than that of the leading end transfer voltage (the first transfer bias) and an absolute value of the tail end transfer voltage (the third transfer bias) can be smaller than that of the leading end transfer voltage (the first transfer bias).
- the controller 190 can sense system resistance by applying a sensing voltage or current to the transferring unit 140 before the leading end of the print medium passes through the transfer nip N.
- the system resistance can correspond to a value reflected by an effect by ambient temperature/humidity and the lifetime of the transferring unit 140 . The lower the ambient temperature/humidity, the higher the system resistance tends to be.
- transfer voltages of 2700 V, 3000 V and 2200 V can be applied to the transferring unit 140 while the leading end region, the middle region and the tail end region of the print medium pass through the transfer nip N, respectively.
- the absolute value of the middle transfer voltage (the second transfer bias) can be larger than that of the leading end transfer voltage (the first transfer bias) and the absolute value of the tail end transfer voltage (the third transfer bias) can be smaller than that of the leading end transfer voltage (the first transfer bias).
- a range classified into HH, NN and LL conditions depending on the ambient temperature/humidity does not have a constant value but may be varied as necessary.
- N conditions Under normal ambient temperature/humidity conditions (referred to herein as “NN conditions”), transfer voltages of 2500 V, 2750 V and 2100 V can be applied to the transferring unit 140 , respectively.
- high ambient temperature (for example, 30° C. or above) and humidity (for example, 80% or above) conditions referred to herein as “HH conditions”.
- transfer voltages of 2200 V, 2350 V and 1900 V can be applied to the transferring unit 140 , respectively.
- the ambient temperature/humidity becomes lower, a difference between the leading end transfer voltage (the first transfer bias) and the middle transfer voltage (the second transfer bias) and a difference between the leading end transfer voltage (the first transfer bias) and the tail end transfer voltage (the third transfer bias) can become increased.
- the controller 190 may control the bias supplying unit 185 to apply the first transfer bias, the second transfer bias having an absolute value larger than that of the first transfer bias, and the third transfer bias having an absolute value smaller than that of the first transfer bias to the transferring unit 140 , respectively.
- the predetermined thickness may be about 90 [g/m 3 ] of basis weight and the predetermined speed may be about 12 ppm.
- the predetermined thickness and the predetermined speed may be varied depending on formation of print convey paths, roller arrangement, ambient temperature/humidity, lifetime (use time) of the transferring unit 140 and/or other design characteristics of the image forming apparatus.
- FIG. 13 is a graph to evaluate whether an image defect or an image concentration difference can be identified in the tail end region of the same kind of print medium by naked eyes when a tail end transfer voltage lower by a voltage difference (dV) than a middle transfer voltage applied while the middle region of the print medium passes through the transfer nip N is applied while the tail end region of the print medium passes through the transfer nip N.
- dV voltage difference
- the voltage difference is ⁇ 400 V under HH conditions, that is, if a tail end transfer voltage lower by about 400 V than a middle transfer voltage is applied, the optimum image quality can be achieved, and, if the tail end transfer voltage lower by about 600 V than the middle transfer voltage is applied under NN conditions, the optimum image quality can be achieved. In addition, if the tail end transfer voltage lower by about 900 V than the middle transfer voltage is applied under LL conditions, the optimum image quality can be achieved. It can be also seen that the voltage difference (dV) is made larger as the ambient temperature/humidity becomes lower.
- FIG. 14 illustrates a pattern of a transfer voltage to be applied to the transferring unit 140 depending on system resistance for a print medium having typical thickness (60 to 90 [g/m 3 ] of basis weight).
- the transferring unit 140 can be an initial article (use time being zero), and the ambient temperature and humidity can be normal temperature and normal humidity (NN conditions), respectively.
- the controller 190 can control the bias supplying unit 185 to apply the leading end transfer voltage (the first transfer bias), the middle transfer voltage (the second transfer bias) and the tail end transfer voltage (the third transfer bias) to the transferring unit 140 , respectively.
- the absolute value of the middle transfer voltage (the second transfer bias) can be smaller than that of the leading end transfer voltage (the first transfer bias) and the absolute value of the tail end transfer voltage (the third transfer bias) can be smaller than that of the middle transfer voltage (the second transfer bias).
- FIG. 15 illustrates a pattern of transfer voltage to be applied to the transferring unit 140 in a case where the general paper is printed in a single-sided print mode under low-temperature and low-humidity conditions (LL conditions).
- the transferring unit 140 can be an initial article.
- the controller 190 can control the bias supplying unit 185 to apply the leading end transfer voltage (the first transfer bias), the middle transfer voltage (the second transfer bias) having an absolute value larger than that of the leading end transfer voltage (the first transfer bias), and the tail end transfer voltage (the third transfer bias) having an absolute value smaller than that of the leading end transfer voltage (the first transfer bias) to the transferring unit 140 , respectively.
- the system resistance becomes larger. As illustrated in FIG. 15 , as the system resistance becomes larger, a variation of the leading end transfer voltage (the first transfer bias) become larger than those of the middle transfer voltage (the second transfer bias) and the tail end transfer voltage (the third transfer bias).
- the image forming apparatus 100 may further include an interface unit 181 connected to a host device such as an external computer, a display unit 182 to display predetermined information to a user, an input unit 183 to receive an input from the user, and a driving unit 184 controlled by the controller 190 to rotate/drive various rollers in the image forming apparatus 100 of FIG. 3 .
- the user interface unit 181 , display unit 182 , and input unit 183 can be integrated with the controller 190 , or can be provided separately in various combinations.
- FIGS. 17A and 17B a control method of the image forming apparatus of the present general inventive concept will be described with reference to FIGS. 17A and 17B .
- an attribute of the print medium can be sensed as illustrated in FIGS. 3 , 5 , 17 A and 17 B (S 10 ).
- first to third regions of the print medium pass through the transfer nip N according to the sensed attribute of the print medium, different first to third biases can be applied to the transferring unit, respectively.
- the first predetermined value may be about 90 [g/m 3 ] of basis weight and may be properly varied as necessary.
- the print medium may be set as a thick print medium, a general print medium and a thin print medium depending on a manufacturer of the image forming apparatus.
- the predetermined speed may be about 12 ppm.
- the predetermined speed can be used to determine whether the convey speed of the print medium, that is, a process speed, is low or high, and thus it is to be understood that the predetermined speed may be set to be a different value other than the specified value.
- the first transfer bias, the second transfer bias having an absolute value larger than that of the first transfer bias, and the third transfer bias having an absolute value larger than that of the second transfer bias can be applied to the transferring unit, respectively, while the leading end region, the middle region and the tail end region of the print medium pass through the transfer nip, at operation S 50 .
- the first transfer bias, the second transfer bias having an absolute value larger than that of the first transfer bias, and the third transfer bias having an absolute value smaller than that of the first transfer bias can be applied to the transferring unit, respectively, while the leading end region, the middle region and the tail end region of the print medium pass through the transfer nip, at operation S 80 .
- the second predetermined value may be about 60 [g/m 3 ] of basis weight and may be varied depending on a manufacturer of the image forming apparatus.
- the first transfer bias, the second transfer bias having an absolute value larger than that of the first transfer bias, and the third transfer bias having an absolute value larger than that of the second transfer bias can be applied to the transferring unit, respectively, while the leading end region, the middle region and the tail end region of the print medium pass through the transfer nip, at operation S 50 .
- the thickness of the print medium is not smaller than the second predetermined value (NO in S 30 ), that is, if the print medium is a print medium having general thickness, it can be determined whether ambient environments are under low temperature/low humidity conditions (LL conditions), at operation S 60 .
- LL conditions low temperature/low humidity conditions
- the first transfer bias, the second transfer bias having an absolute value larger than that of the first transfer bias, and the third transfer bias having an absolute value smaller than that of the first transfer bias can be applied to the transferring unit, respectively, while the leading end region, the middle region and the tail end region of the print medium pass through the transfer nip, at operation S 80 .
- the first transfer bias, the second transfer bias having an absolute value smaller than that of the first transfer bias, and the third transfer bias having an absolute value smaller than that of the second transfer bias can be applied to the transferring unit, respectively, while the leading end region, the middle region and the tail end region of the print medium pass through the transfer nip, at operation S 70 .
- a posture of the print medium that is, an entrance angle of the print medium into the transfer nip N
- the first transfer bias can be applied to the transferring unit 140 .
- the change of posture of the print medium can be interpreted to mean that the print medium deviates from a designed normal path and passes through the transfer nip N along a different path. That is, the change of posture of the print medium can mean a change of the entrance angle of the print medium into the transfer nip N.
- a point of time when the posture of the print medium is changed may be indirectly predicted by finding at which point from the leading end of the print medium that the posture of the print medium is changed, or at which point of time that the posture of the print medium is changed from time when the leading end passes through the transfer nip through a plurality of experiments.
- the point or the point of time that the posture of the print medium is changed can be stored in a memory (not illustrated) of the image forming apparatus 100 .
- the first transfer bias can continue to be applied to the transferring unit 140 , at operation S 130 .
- the second transfer bias having an absolute value smaller than the first transfer bias can be applied to the transferring unit 140 , at operation S 160 . Accordingly, it is possible to prevent a transfer electric field from being excessively increased due to rapid charging as the one region of the print medium moves along the over-transfer path C, and thus prevent image defects such as image picking.
- the second transfer bias having an absolute value larger than that of the first transfer bias can be applied to the transferring unit 140 while the one region of the print medium passes through the transfer nip N, at operation S 170 .
- a transfer electric field can become insufficient, and accordingly, by applying the stronger second transfer bias to the transferring unit 140 to supplement the insufficient transfer electric field, it is possible to prevent image defects such as image omission.
- the operations S 120 to S 170 can continue to be performed until one page of the print medium completely passes through the transfer nip, at operation S 180 .
- the above-described transfer bias application method is not limited thereto, and may be applied to a direct transfer system in which the transferred unit becomes the image carrier itself. More specifically, in a direct transfer system in which the image carrier opposes the transferring unit with the print medium interposed therebetween and the visible image of the image carrier is transferred onto the print medium, the transfer biases may be applied to the transferring unit according to the above-described transfer application method. That is, in the direct transfer system, the transferred unit can correspond to the image carrier.
Abstract
Description
Claims (14)
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US13/155,511 US8160465B2 (en) | 2008-08-22 | 2011-06-08 | Image forming apparatus and control method thereof |
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KR1020080082494A KR101302057B1 (en) | 2008-08-22 | 2008-08-22 | Image forming apparatus and control method thereof |
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US12/511,127 US7983580B2 (en) | 2008-08-22 | 2009-07-29 | Image forming apparatus and control method thereof |
US13/155,511 US8160465B2 (en) | 2008-08-22 | 2011-06-08 | Image forming apparatus and control method thereof |
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US12/511,127 Continuation US7983580B2 (en) | 2008-08-22 | 2009-07-29 | Image forming apparatus and control method thereof |
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US13/155,511 Active US8160465B2 (en) | 2008-08-22 | 2011-06-08 | Image forming apparatus and control method thereof |
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JP5713590B2 (en) * | 2010-07-01 | 2015-05-07 | キヤノン株式会社 | Printing apparatus, printing apparatus control method, and program |
JP6261335B2 (en) * | 2013-12-27 | 2018-01-17 | キヤノン株式会社 | Image forming apparatus |
US9110408B1 (en) * | 2014-02-24 | 2015-08-18 | Xerox Corporation | Adjusting tone reproduction curve and belt tension to control printing errors |
JP6355021B2 (en) * | 2014-06-25 | 2018-07-11 | 株式会社リコー | Image forming apparatus |
US9529316B2 (en) * | 2014-10-31 | 2016-12-27 | Brother Kogyo Kabushiki Kaisha | Image forming apparatus |
JP6868179B2 (en) * | 2016-10-21 | 2021-05-12 | 富士フイルムビジネスイノベーション株式会社 | Image forming device |
JP2018128620A (en) * | 2017-02-10 | 2018-08-16 | キヤノン株式会社 | Image forming apparatus |
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JP2001051527A (en) | 1999-08-16 | 2001-02-23 | Fuji Xerox Co Ltd | Transfer controlling device for image forming device, and monitor processing device used for the same |
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JP4532879B2 (en) * | 2002-11-08 | 2010-08-25 | キヤノン株式会社 | Image forming apparatus |
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KR101302057B1 (en) | 2013-09-05 |
US20110236044A1 (en) | 2011-09-29 |
US7983580B2 (en) | 2011-07-19 |
US20100046969A1 (en) | 2010-02-25 |
KR20100023622A (en) | 2010-03-04 |
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